Glass-ceramic composition for recording disk substrate

Abstract

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 47.5 to 52.5 wt % of SiO 2 , from 10 to 30 wt % of Al 2 O 3 , from 10 to 30 wt % of MgO, and from 6.2 to 7.8 wt % of TiO 2 .

What is claimed is:  
     
       1. A glass ceramic composition for recording disk substrate consisting essentially, expressed in terms of weight percent on an oxide basis, of 
       from 47.5 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.8 wt % of TiO 2 ,  
       wherein the glass ceramic composition includes a main crystalline phase of magnesium alumina silicate crystal.  
     
     
       2. A glass ceramic recording disk substrate, wherein the glass ceramic is prepared from a composition which consists essentially, expressed in terms of weight percent on the oxide basis, of 
       from 47.5 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.8 wt % of TiO 2 ,  
       wherein the glass ceramic includes a main crystalline phase of magnesium alumina silicate crystal.  
     
     
       3. A glass ceramic composition for recording disk substrate consisting essentially, expressed in terms of weight percent on an oxide basis, of 
       from 50.0 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.8 wt % of TiO 2 .  
     
     
       4. A glass ceramic recording disk substrate, wherein the glass ceramic is prepared from a composition which consists essentially, expressed in terms of weight percent on the oxide basis, of 
       from 50.0 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.8 wt % of TiO 2 .  
     
     
       5. A glass ceramic composition for recording disk substrate consisting essentially, expressed in terms of weight percent on an oxide basis, of 
       from 47.5 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.0 wt % of TiO 2 .  
     
     
       6. A glass ceramic recording disk substrate, wherein the glass ceramic is prepared from a composition which consists essentially, expressed in terms of weight percent on the oxide basis, of 
       from 47.5 to 52.5 wt % of SiO 2 ,  
       from 10 to 30 wt % of Al 2 O 3 ,  
       from 10 to 30 wt % of MgO, and  
       from 6.2 to 7.0 wt % of TiO 2 .  
     
     
       7. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of P 2 O 5 .  
     
     
       8. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Nb 2 O 5 .  
     
     
       9. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Ta 2 O 5 .  
     
     
       10. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 12 wt % of Li 2 O.  
     
     
       11. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 12 wt % of ZrO 2 .  
     
     
       12. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of B 2 O 3 .  
     
     
       13. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Y 2 O 3 .  
     
     
       14. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of K 2 O.  
     
     
       15. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of Sb 2 O 3 .  
     
     
       16. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of ZnO.  
     
     
       17. A glass ceramics composition as claimed in  claim 1 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of La 2 O 3 .  
     
     
       18. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of P 2 O 5 .  
     
     
       19. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Nb 2 O 5 .  
     
     
       20. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Ta 2 O 5 .  
     
     
       21. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 12 wt % of Li 2 O.  
     
     
       22. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 12 wt % of ZrO 2 .  
     
     
       23. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of B 2 O 3 .  
     
     
       24. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 9 wt % of Y 2 O 3 .  
     
     
       25. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of K 2 O.  
     
     
       26. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of Sb 2 O 3 .  
     
     
       27. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of ZnO.  
     
     
       28. A recording disk substrate as claimed in  claim 2 , wherein said glass ceramic composition further consists essentially, expressed in terms of weight percent on an oxide basis, of 
       from 0.1 to 5 wt % of La 2 O 3 .